In general, a discharge lamp apparatus having a lighting control unit (hereafter, referred to as a ballast) outside of a lamp housing is provided with a connector for electrically connecting the ballast and an inside of the lamp housing. This kind of discharge lamp apparatus is known in Japanese Unexamined Patent Publications No. 9-289383 and No. 10-51158, for example.
In such a discharge lamp apparatus, it is known to provide a sealing member around the connector to prevent condensation, which is generated in the lamp housing due to heat of a discharge lamp, from entering a ballast housing. However, if the sealing member is deteriorated over time and a sealing effect is reduced, condensation or water vapor generated in the lamp housing is likely to be sucked into the ballast housing through deteriorated portion of the sealing member when the temperature inside the ballast housing is lowered. As a result, a ballast circuit board housed in the ballast housing and terminals of components mounted on the ballast circuit board may be corroded.
Also, it is known to form a ventilation hole in the connector for allowing communication between the ballast housing and the lamp housing. The ventilation hole functions to release heat generated from electrical components and electronic parts mounted on the ballast circuit board outside of the ballast housing, thereby suppressing a temperature increase in the ballast housing.
Also in this structure, however, condensation or water vapor generated in the lamp housing is likely to be sucked in the ballast housing through the ventilation hole when the temperature inside the ballast housing is lowered. This may result in corrosion of the ballast circuit board and terminals of the components installed in the ballast circuit board.